Salmonellosis is one of the main causes of bacterial gastroenteritis in humans (Brenner, et al. 2000). Each year, 93.8 million cases are reported globally, giving high indices of morbidity and mortality (155 000 deaths/year) (Majowicz, et al. 2010; Cabrera, 2008). In the United States it is estimated that 40% of the infections caused by Salmonella occur in children under 10 years (Angulo, et al. 2004). Treatment of this disease imposes a considerable economic burden on many countries; according to the United States Department of Agriculture (USDA), the annual cost for treating salmonellosis, including loss of productivity, in 2005 was 2.3 billion dollars (Atterbury, 2007). Usually these pathogens cause mild and moderate gastroenteritis, but in more severe cases they may cause septicemias (Zhao, et al. 2001).
Transmission of Salmonella is mainly due to consumption of contaminated foods, in particular by consuming poultry products, which are widely accepted as the main source of infection with this bacterium (Atterbury, 2007).
The USDA estimates that 50-75% of the cases of salmonellosis are due to the purchase of contaminated poultry products, in particular through consumption of chicken and eggs. The most prevalent serovars worldwide include Salmonella enteritidis (64.5%) and Salmonella typhimurium (16.5%) (WO2004071324 A2; EP 2 550 870 A1). However, in 2010 the group for Integrated Investigation and Vigilance of Antimicrobial Resistance—COIPARS of the Colombian Corporation for Agricultural Research—CORPOICA, after reporting a prevalence of Salmonella of 41% in chicken-producing farms and 26% in chicken at points of sale, found that the serovars of Salmonella paratyphi B and Salmonella Heidelberg were the most prevalent in farms in Colombia (Donado-Godoy, et al. 2012). Regarding Salmonella paratyphi B, there was a prevalence in farms of 76% and in meat at points of sale of 51%, whereas Salmonella Heidelberg had a prevalence of 23% and 16%, respectively (Donado-Godoy, 2010). This report was of great importance in the sector since it was the first time that Salmonella paratyphi B had been reported in the food chain of the poultry sector. Based on this publication, a study was conducted in which isolates of Salmonella were serotyped at various points of the poultry chain, including workers in the sector. As a result, the serotypes isolated from farms and abattoirs were exactly the same as found in humans, company workers (personal communication). The earlier study shows that the increase in serotypes isolated as Salmonella paratyphi B are reaching humans and therefore may be generating new outbreaks of a pathogenic Salmonella that was not being controlled and that may become a new public health problem.
One of the reasons why there is a high prevalence of Salmonella in foods of poultry origin is due to their capacity for colonizing the intestine of chicken; in the case of Salmonella enteritidis, Salmonella typhimurium and Salmonella paratyphi B, they do not produce infection or visible symptoms in the bird and they have the capacity to colonize the interior of eggs. However, they cause disease in humans who consume contaminated poultry products because Salmonella crosses the intestinal barrier, destroying the microvilli of the epithelial cells and in consequence affecting the capacity for absorption (Zhao, 2002; Keller, et al. 1995).
Control of Salmonella in the poultry chain has been based historically on a combination of biosafety in the farm, taking appropriate sanitary measures for housing, production and marketing, in addition to the use of antimicrobials and vaccines (Atterbury, 2007). Contamination in poultry farms is the result of infected birds and cross contamination in the production chain (San Myint, 2004; Carrasco, et al. 2012). Cross contamination occurs owing to failure to implement good manufacturing practice, where lack of hygiene, and mistakes in the steps of refrigeration and transport of the products, mean that the conditions of biosafety in the production chain are not the most appropriate (Carrasco, et al. 2012; San Myint, 2004). In any case, the initial source of contamination by Salmonella is due to the state of the infected poultry. The importance of the foregoing lies in control of the bacterium from its initial inoculum, so as to reduce contamination by Salmonella in the subsequent steps of the production process for poultry-based food products (San Myint, 2004).
The cost of the treatments that are used for reducing Salmonella in chicken farms and in foods is high because they are widely distributed pathogens and they colonize easily (Zhao, 2002; WO 2004071324 A2). That is why various treatments have been implemented for controlling and reducing these pathogens such as the use of chlorinated water in sprays, physical treatments such as steam cleaning, dry heat and ultraviolet light, and the use of chemical additives. However, in some cases it has been reported that the organoleptic quality of the final product may be affected (Garcia, et al. 2008). Regarding the use of disinfectants, these have been used for eradicating the pathogens and for reducing cross contamination during the production process, but the appearance of resistance and the environmental consequences mean that it is not fully effective (Goode, et al. 2003). Another treatment widely used throughout the world for controlling Salmonella serovars in the poultry industry is vaccination. There are reports that show cases of low efficiency, since the vaccines that are used most are made from inactivated or attenuated reference strains that do not cover all of the serotypes present in all poultry farms (Zhao, 2002; Vandelplas, et al. 2010). Moreover, the vaccines are only directed at controlling Salmonella enteritidis and Salmonella typhimurium, but not Salmonella paratyphi B, a new emerging pathogen in the Colombian poultry sector, and that has previously occurred in several European countries, which makes its control even more difficult (Donado-Godoy, et al. 2012; Van Immersel, et al. 2004).
Antimicrobials have been used in agriculture since the beginning of 1950 for treating bacterial infections and to improve feed efficiency both in the cattle-raising sector and in the poultry sector (Angulo, et al. 2004). In recent years, the overuse of antimicrobials in the poultry industry has resulted in the appearance of Salmonella strains that are resistant to these medicinal products (INS, 2011). The problem is that most of them are used for controlling bacteria in animals for human consumption and in hospitalized patients who require clinical treatment. As a result, this increases the probability of zoonotic bacteria developing resistance to the medicinal products used in humans (Angulo, et al. 2004). The emergence of multi-drug resistant (MDR) Salmonella strains is of great concern to the medical and veterinary professions, since according to epidemiological studies, the commonest source of MDR strains in humans is due to the consumption of contaminated foods of animal origin (O'Flynn et al., 2006).
Faced with the need for new strategies for controlling, eliminating and/or reducing Salmonella in the poultry industry, phage-therapy has become very important in recent years since the results are promising. Bacteriophages are viruses that kill bacteria and they are widely distributed in all types of environments. Their use has proved to be an effective method for controlling zoonotic bacteria, since they have unique advantages compared to the antimicrobials (Atterbury, 2007). The advantages of phage-therapy include specificity, and bacteriophages may be strain-specific or species-specific. This characteristic is of great importance because it avoids the imbalance of the intestinal microbiota, contrary to that frequently caused by broad-spectrum antimicrobials (Atterbury, 2007; Kutter & Sulakvelidze, 2005). Also, the bacteriophages replicate while the bacterium is viable, i.e. when it is eliminated, the phages are naturally self-limiting (Atterbury, 2007). Bacteriophages are not toxic to animals or humans, as they only attack bacteria. On the other hand they have the capacity to increase their initial concentration, so that on infecting bacteria they multiply within them until they are eliminated (Kutter & Sulakvelidze, 2005; Summers, 2001); the advantage obtained from the aforementioned process is reduction of the initial doses necessary for eliminating the bacterial contaminations.
In this connection, various compositions have been reported that comprise specific phages or combinations of phages that are used for controlling bacteria, especially Salmonella. One of the cases reported corresponds to patent WO2013024304, which discloses the use of bacteriophages for lysis of the bacterium Salmonella. That document discloses compositions that comprise bacteriophages selected from ΦSH17, ΦSH18, ΦSH19 or a variant of one of these bacteriophages, wherein the variant retains the phenotypic characteristics of the parent bacteriophage. Moreover, patents US20090297561, WO2005024005, U.S. Pat. No. 8,293,515, U520080118468, U520130336932, U.S. Pat. Nos. 8,685,696, 8,597,928 and WO2013014273 describe various types of bacteriophages that have specific activity against Salmonella and that are used, moreover, for preparing compositions useful for control, and treatment of infection in animals or humans as well as in the colonization of processed and unprocessed food products by Salmonella, or colonization of equipment involved in the processing of said food products.
Moreover, patent RU2232808 teaches a biological preparation for treating and preventing salmonellosis in farm animals and poultry, wherein said biopreparations contain various strains of bacteriophages, which are used in an effective amount.
In this class of ideas, patent WO2013169102 relates to a bacteriophage, a polypeptide and a corresponding polynucleotide, a nucleic acid molecule and/or vector and/or cell that comprises said polynucleotide, a composition that comprises said bacteriophage, polypeptide, polynucleotide, construct, vector and/or cell, for the prevention, treatment or diagnosis of contamination with Salmonella. 
Finally, there are also documents such as patent US20140220659, which discloses a method for preparing a strain of bacteriophages specific to a selected bacterial strain, strains of bacteriophages obtained in this way and the use of bacteriophages for preparing a preparation for the prevention and treatment of infections of farm animals, especially poultry, with strains of pathogenic bacteria that are sensitive to these bacteriophages. Moreover, this document provides technology for production of an antimicrobial preparation suitable for use as a feed additive for poultry and pigs, which at the same time is specific to the pathogenic strains of Salmonella that cause the occurrence of salmonellosis, especially in human beings.